Overview

Potassium (K+) is an important ion in the body. K+ is found mainly intracellularly (inside the cells) whereas sodium (Na+) is found extracellularly (outside the cells).

• Serum Potassium: 3.5mmol/L – 5.0mmol/L
• Serum Sodium:

Therefore:

• Hyperkalaemia: >5mmol/L
• Hypokalaemia: <3.5mmol/L

As the pH rises , K+ is shifted intracellularly and the serum levels falls; conversely when serum pH decreases, intracellular K+ shits extracellularly into the vascular space and so the serum level increases. This is because H+ and K+ are both positive and it is important to have normal +ions levels in the serum to maintain a gradient across the cell membrane to maintain the excitability of nerve and muscle cells, including the myocardium.

Causes of Hyperkalaemia

• Excessive intake
• Increased production
  • Haemolysis
  • Rhabdomyolysis
  • Intense physical activity
  • Burns
  • Tumour lysis syndrome
• Shift from intracellular to extracellular fluid
  • Acidosis
  • Insulin deficiency/resistance
  • Medications
    • β-blocker
    • Suxamethonium
    • Digoxin
    • Spironolactone
  • Hyperkalaemic periodic paralysis
• Decreased excretion
  • Renal failure
  • Addison’s disease
  • Medications
    • Potassium sparing diuretics
    • ACE inhibitors
    • NSAIDs
    • Trimethoprim, cyclosporin, tacrolimus

Signs and symptoms

• Non-specific
• Generalised muscle weakness
• Respiratory depression
• Ascending paralysis
• Palpitations, Arrhythmia, Cardiac arrest
  • ECG CHANGES:

Management

Management – nonpharmacological

• ECG
• ABCD
• Check serum potassium

Management – pharmacological

• IV Frusemide (provided patient normal urine output)
• IV Calcium chloride or Calcium gluconate
• Drive K+ into the cell
  • Insulin + Glucose
  • Salbutamol
  • Sodium bicarbonate – if acidotic
• Monitor serum K+ every hour
• Eliminate K+ from the body
  • Calcium Resonium (this is slow)
  • Dialysis (last line)

Complications of Hyperkalaemia

• Cardiac arrest
• Weakness
• Paraesthesiae
• Decreased reflexes
• Ascending paralysis

Hypokalaemia

Defined as potassium <3.5mmol’L

Signs and symptoms

• Generalised muscle weakness
• Respiratory depression
• Ascending paralysis
• Ileus, constipation
• Palpitations, Arrhythmia, Cardiac arrest
• Nephrogenic diabetes insipidus (characterised by polyuria and polydipsia)

Management

Management – nonpharmacological

• ECG
• ABCD
• Check serum potassium

Management – pharmacological

• Chlorvescent – Given STAT
• Slow K
• Potassium Chloride (KCl) IV given in 10mmol in 100ml of normal saline
• Check serum potassium

ECG findings

• Peaked P waves
• T wave flattening and inversion
• U waves